Wind energy harvesting from transport systems: A resource estimation assessment

Many recent patents worldwide address the concept of harvesting wind energy from aerodynamic losses in motorways, however the mechanics of a specific device dedicated to the task has never been described. The lack of a characterization of the energy resource likely explains why the international market is still to acknowledge any technology related to the concept. Here, an experimental activity is presented to investigate the flow field generated by traffic in motorways and eventually develop an innovative technology that complies with emerging energy policies. In the case of traffic source, the energetic rationale seems to have a double motivation: there will always be an optimal energy supply associated with an increment in transport demand and, contrary to other renewables, the transport aerodynamic losses belong to a source of costs, making them a remarkably sustainable energy source. After a thorough analysis of the correlation between truck flow and wind speed classes, the characterization of a resource indicator for time of wind above a cut-in speed is given, with an account for the effects of traffic clusters and traffic related wind-drops. We demonstrate how during weekdays daytime hours the traffic-generated resource can allow an energy conversion beyond a threshold possibly permitting a positive energetic balance of the system. A study on the effect of traffic related wind-drops is also carried out to investigate how the issue could be relevant in the transient behavior and ultimately in the performance of a mini wind turbine in the kW-range. While many findings relate to the motorway site where the campaign was sited, fitting of the experimental data to the generic motorway case permits to explore a complete range of traffic flows.